Solvent and Temperature Effects on Spectral Properties of Two Poly(3-alkyl)thiophene Derivatives

Two alkyl substituted polythiophene derivatives: poly(3-hexylthiophene)(P3HT) and poly(3-decylthiophene)(P3DT), have synthesized by oxidation coupling polymerization of 3-alkylthiophene using iron(III) chloride as catalyst in chloroform. While both polymers in pure chloroform solution have maximum absorption at approximately same wavelength of 440nm, they behave differently with respect to changes observed on their UV-visible and photoluminescence spectra when the quality of the poor solvent is changed in good solvent (chloroform) / poor solvent (methanol) mixtures. With increasing volume fraction of methanol in mixtures, the absorption spectra of P3HT and P3DT red-shift, peaking at maximum wavelength of 495nm (P3HT) and 510nm(P3DT). Furthermore, the absorption spectra of the two polymers in chloroform blue-shift as the temperature rises. P3HT shows 4.73nm blue-shifts at 50℃ in contrast to the case at 20℃, while P3DT blue-shifts about 5.04nm. The photoluminescence spectra of the two polymers in mixed solution are also investigated, which show that the luminescence spectra shift to longer wavelength with an accompanying drop in the PL intensity as methanol is increased. The absorption and emission spectra of the two polymers in a poor solvent and a thin film are similar, which indicate that a similar longer conjugation length in the two cases. It could conclude that the polymers exist almost the same conformations and aggregations in both a poor solvent and a thin film. P3DT exhibits more sensitive spectra properties (big red-shifts in both absorption and luminescence spectra in poor solvents and large blue-shifts at high temperature) with contrast to P3HT, which imply that long side alkyl may improve the chromic properties of the polymer.

Low-cost and efficient organic solar cells based on polythiopheneand poly(thiophene vinylene)-related donors

At present,most of state-of-the-art power conversion efficiencies(PCEs)of organic solar cells(OSCs)are achieved from the photoactive materials involving donor–acceptor(D–A)copolymer donors.It is well known that the complicated molecular structure of D–A copolymers means the tedious synthesis,which brings about severe cost issue and poor scalability for the industrial production.Therefore,to develop application-oriented OSCs,considerable attention should be paid on simplifying the chemical structures of polymer donors.Polythiophene(PT)and poly(thiophene vinylene)(PTV)derivatives should be among the simplest polymer donors,and OSCs based on them have made some breakthroughs in past 2 years.Here,we briefly introduce the recent advances of OSCs based on low-cost polymers including poly(3-hexylthiophene)(P3HT),PT derivatives,and PTV derivatives,respectively,and emphasize the importance of modulating energy levels,preaggregation effect,and D/A miscibility for the past progress as well as the future development.At last,we also propose some challenges demanding prompt solution for realizing practical application of OSCs,aiming at providing guidance and stimulating new ideas for further research.

Synthesis of Highly Regioregular, Head-to-Tail Coupled Poly(3-octylesterthiophene) via C―H/C―H Coupling Polycondensation

Highly regioregular, head-to-tail coupled poly（3-octylesterthiophene） was synthesized by the Pd-catalysed oxidative C--H/C--H coupling polycondensation. The regioregularity of polymer products was confirmed by the 1H-NMR technique. Furthermore, the effects of various reaction factors including polymerization temperature, solvents and catalysts etc. on the yield, molecular weight and structural regioregularity of the resultant polymers were systematically studied. The optical, electrochemical and crystallization properties of the resultant P3OET with different HT regioregularities in solution and film state were studied by UV-Vis and fluorescent spectroscopy, cyclic voltammetry and X-ray diffraction （XRD）, resepectively.